The brain’s duck test in phantom percepts: multisensory congruence in
chronic pain and tinnitus
Chronic neuropathic pain and chronic tinnitus have been likened to
phantom percepts, in which a complete or partial sensory deafferentation
results in a filling in of the missing information derived from memory.
150 participants, 50 with tinnitus, 50 with chronic pain and 50 healthy
controls underwent a resting state EEG. Source localized current density
was recorded from all the sensory cortices (olfactory, gustatory,
somatosensory, auditory, vestibular, visual) as well as the
parahippocampal area. Functional connectivity by means of lagged phase
synchronization was also computed between these regions of interest.
Pain and tinnitus were associated with gamma band activity, reflecting
prediction errors, in all sensory cortices except the olfactory and
gustatory cortex. Functional connectivity identified theta frequency
connectivity between each of the sensory cortices except the chemical
senses to the parahippocampus, but not between the individual sensory
cortices. When one sensory domain is deprived, the other senses may
provide the parahippocampal ‘contextual’ area with the most likely sound
or somatosensory sensation to fill in the gap, applying an abductive
‘duck test’ approach, i.e., based on stored multisensory congruence.
This novel concept paves the way to develop novel treatments for pain
and tinnitus, using multisensory modulation or via parahippocampal